Power Switch Short-Circuit Detection via Stray Inductance Sensing
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Solution Overview
Problem
Conventional methods for detecting short circuits in gate-controlled power switches, such as silicon carbide (SiC) and gallium nitride (GaN) MOSFETs, are temperature-dependent, require careful design, and may not detect failures quickly enough to prevent damage, especially in high-stress scenarios.
Innovation Solution
A fast short circuit detection method using a measurement circuit to monitor the voltage drop across stray inductance of the gate-controlled power switch, generating a detection signal when the voltage exceeds a reference level during the switch-on state, triggering an automatic switch-off by the gate driver circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional saturation detection method is used, then short circuit detection is achieved, but detection speed is slow and temperature-dependent
Solution Approach 1:
The invention extracts the detection function from the main power switching circuit by using a separate measurement circuit that monitors voltage at the source terminal. This isolation allows independent optimization of detection speed without affecting the main power switch performance, achieving fast detection within 300 nanoseconds while maintaining reliability.
Solution Approach 2:
The patent introduces an intermediary measurement circuit with a dedicated voltage sensing path that mediates between the power switch and the control system. This intermediary structure provides isolated voltage information for fast detection without requiring direct intervention in the main power circuit, eliminating temperature dependence and reducing detection time.
2Reliability
If direct current measurement is performed, then short circuit detection is achieved, but device complexity increases
Solution Approach 1:
The invention extracts only the essential voltage sensing function needed for short circuit detection, implementing a minimal measurement circuit that monitors source terminal voltage. This extraction approach avoids the complexity of direct current measurement while maintaining detection accuracy through simple voltage threshold comparison.
Solution Approach 2:
The measurement circuit utilizes the existing source terminal voltage of the power switch itself for detection, rather than requiring separate sensing components. The power switch's own voltage characteristics serve the dual purpose of normal operation and fault detection, simplifying the overall device structure while maintaining reliability.
3Reliability
If conventional detection methods are used, then short circuit detection is achieved, but false positives occur during normal operation
Solution Approach 1:
The invention applies local quality by monitoring voltage at the specific source terminal location rather than using general circuit parameters. This localized measurement approach captures the actual conditions at the power switch source terminal, enabling accurate distinction between normal operation voltage variations and genuine short circuit conditions, thereby eliminating false positives.
Solution Approach 2:
The patent uses a voltage threshold that is set below normal operating voltages but above short circuit voltages, applying partial detection action only when the voltage exceeds this specific threshold. This selective threshold-based approach ensures that normal operation never triggers false positives while still detecting actual short circuits, achieving perfect specificity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables rapid detection of short circuits within 300 nanoseconds, improving the reliability of power electronic systems by preventing damage to SiC and GaN power switches, and reducing false positives during normal operation.
Implementation Method 1
A fast short circuit detection method using a measurement circuit to monitor the voltage drop across stray inductance of the gate-controlled power switch
Data Source
AI summary
A fast short circuit detection method for detection of a short circuit at a gate-controlled power switch, said method comprising the steps of providing a measurement signal in response to a voltage drop along a stray inductance of the gate-controlled power switch; and generating a short circuit detection signal if the provided measurement signal exceeds a reference voltage and the gate-controlled power switch is in a switched-on state.